Which forager type would typically get the best balance of nutrients from their food?
Animal foragers
Carnivore foraging
Carnivore prey items contain essentially the same mix of nutrients
Foraging success is often assumed to be limited by prey availability (quantity)
- Rather than nutritional balance (quality).
Carnivore Foraging: Quanitity vs Quality
- Food quantity driving consumption rates, and thus predator-prey populations, is often challenged
- Lotka Voltera vs Optimal Foraging
Case study #1: Wolf spiders, prey quality and consumption
- Wolf spiders feed near standing water in California (Greenstone 1979)
- 80% of the diet is shore flies, water boatmen and mosquitoes
- Prey species were marked as either present or absent in each spider gut
- spiders classified into groups (answer Q1)
- Spider stomach contents (total N = 1226) from 13 different pools of water
- Spiders from 7 out of 13 pools were more likely than by chance to have consumed all 3 prey
- polyphagy (eat a variety of food)
- answer Q2
- Side note: Can you imagine making graphs without modern computers!!!
Leveling up with Mayntz et al. 2005
- Hypothesis: IF wolf spiders optimize nutrient intake, THEN they should choose a prey type that remedies a prior nutritional deficiency
- experiment manipulating findings from Greenwood (1979)
- Nutritional state of the Wolf spiders manipulated by feeding them a pre-treatment diet
- fruit flies with high or low ratio of protein to lipid for 1-2 days.
- Then tested feeding responses to the pre-treatment food and/or a complementary alternative
- offered only 1 choice (same or different prey)
- recorded how much of each was eaten
- answer Q3
Leveling up with Mayntz et al. 2005 (answer Q4)
Today: Quantitative reasoning practice
- In your groups, work through interpretation of the results from these papers
- Use your knowledge of species interactions and evolution to theorize about more complex predator-prey relationships
- These are great practice exam questions!!!